code: def call(self, attr_name, value):
      super().call(attr_name, value)
  
      if value[0] not in {"+", "-"}:
          raise ValueError(
              f'{attr_name} must be prefixed with "+" or "-" to indicate ascending or descending order'
          )
  
imports: from abc import ABC, abstractmethod
  from typing import TypeVar, Union
label_desc: Use image node_id 2 for calling the OrderString obj's underlying member method code with example usage: obj.call(attr_name, value) without return types